This invention relates to an apparatus for determining flow characteristics of Newtonian and non-Newtonian fluids which can be used even at high temperatures and high pressures, independently of flow conditions, with materials high in sol id matter, because of its uncomplicated and sturdy construction; and which can also be used with materials which tend to coagulate, solidify, or crust, because of its self-cleaning action.
Falling ball, or sphere, viscometers, rotation viscometers, oscillation viscometers and capillary viscometers are known from prior art for determining flow characteristics.
Falling sphere viscometers can produce exact viscosity values only for Newtonian fluids, they measure only in a discontinuous manner and they cannot be used in high temperatures, under high pressures and in manufacturing processes.
Rotation viscometers can also measure non-Newtonian fluids. However, they fail when measuring tested substances which tend to settle or solidify or have high solid matter content. Further, with highly volatile fluids, an open surface negatively influences any measured results. Under processing conditions, their measured results are dependent upon flow conditions; thus, using them for testing different substances is possible only to a limited degree and can be accomplished only by interfering with viscometer flow. Particular problems arise at high pressures.
Oscillation viscometers do not involve a viscometer flow, with inertia-reaction forces and surrounding conditions not allowing exact viscosity measurements. Thus, only relative values are determined. An oscillation viscometer is not suitable for fluids which form sediments or which contain solid matter.
Prior-art capillary viscometers measure only discontinuously (e.g. measuring takes place after cleaning, filling and tempering (warming or cooling) of a storage container) or continuously in a by-pass manner wherein a defined volume flow is moved along a test path with the help of a gear pump. It is a disadvantage of this arrangement that long reaction times are required and that the gear pump fails when dealing with materials which contain solid matter and which tend to stick.
A further apparatus for measuring viscosity is described in German patent document DE-OS 33 31 659. This apparatus has the following disadvantages:
A measured value is dependent upon an environmental pressure, thus devices for generating a positive or a negative pressure are required. A measuring procedure for this device can be used only in pressure-less containers and cannot be used in high temperatures or with high mechanical loads. Flow in capillaries of this apparatus is dependent upon a fill level of a fluid in a measuring container and a measuring range is limited by a maximum achievable negative pressure.
Still another operating principle is described in DE-OS 32 37 130. Use of spring-bellows capillary viscometers poses a problem in particular with fluids containing ferrite matter because they employ electric solenoids. Also, an exchange of tested substances is not ensured and flow conditions inside capillaries thereof are not stable because of an exponential time curve of a bellows stretch.
It is an object of this invention to provide an apparatus for exactly measuring flow characteristics of fluent materials in pipes, containers and receptacles independently from pressure and flow conditions as well as from mounting positions of the viscometer. An application of the device of this invention is possible even under extreme environmental, mechanical and climatic loads.